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**aaronwt6** · 12-09-2014, 08:20 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Oh, and I'm quite confident in my Y-SUS repair unless the new IPM has a problem. I've fixed at least 20 of these boards.

**aaronwt6** · 12-09-2014, 03:40 PM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Any opinions on this? I'm kinda wondering if it could be a voltage issue. The screen was very bright and the bad X-SUS boards I've seen on this usually cause it to be dim. I'll be home later this evening to toy with it some more.

**mmartell** · 12-10-2014, 12:54 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

I believe there is a 15v or maybe 18v line produced on the ysus that gets routed through the control board and used on the zsus ipm. Verify that it is present on the zsus. I had a similar situation after repairing a zsus ipm only to find the cable from the control board became unseated enough from plugging/unplugging at the zsus to remove the 15v line.

**aaronwt6** · 12-10-2014, 06:39 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Thanks mmartell. I will check that out this evening. Verified that all the voltages were correct and matched the panel label last night but I'll look in to the connections on the logic board.

**tom66** · 12-10-2014, 06:44 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Do you have a scope available?

**aaronwt6** · 12-10-2014, 07:47 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Sure don't Tom. I've been considering picking one up at some point with all the repairs I've been doing but the budget hasn't allowed for it. I do have a spare of each part for this TV other than the X-SUS and Y-SUS. Obviously a known working X-SUS board at this point would be nice to rule that out. Like I said, in my experience with TVs containing this panel, the bad X-SUS typically creates a very dull lit screen. This one is certainly not acting that way.

**aaronwt6** · 12-11-2014, 08:14 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Checked voltages out last night on this. Everything was pretty close to the panel specs. I think I may try a different logic board in it simply because I have one on hand. I noted last night that with no input connected the screen is approx. 90% pure white with small moving black blobs appearing randomly at times. Of course, the screen should be black with the no signal message. That in itself is making me think it has a control issue. I'll update when I have more time to tinker.

**aaronwt6** · 12-11-2014, 08:19 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Tom, if you don't mind too when you get a chance; Could you recommend a scope for me? Certainly don't need anything over the top on price but just whatever you would think is adequate.

Thanks as always,

Aaron

**tom66** · 12-11-2014, 08:28 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

What's your budget?

A scope suitable for most plasma repairs could be had for under $50.

Some high speed stuff, or more detailed diagnosis, can't go wrong with the Rigol DS1054Z. ($399 - put it on the xmas wish list...) fully digital so can play/pause and capture glitches etc., very useful for tracking down intermittent faults. The DS1054Z can also be upgraded to the DS1104Z with all options including deep memory through a simple trick.

I have a top spec DS1074Z (70MHz variant, upgraded to 100MHz; bought it before 50MHz was an option)

**aaronwt6** · 12-11-2014, 08:30 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

I was considering possibly going up as high as $500 if I had to. Really didn't know I could get something adequate for under $100 though. Sounds very encouraging.

**tom66** · 12-11-2014, 08:34 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Well, as I said, it will be a basic analog scope for $50~$100 (that would be a second hand price) so you have no advanced triggers, play/pause etc. but it can be used to check if the Z-sus and Y-sus outputs look approximately OK but you will have to make do with an unstable display due to lack of suitable triggers.

If your budget does go $400+ the Rigol will not steer you wrong, it's an excellent beginner and mid-class instrument. Since it has a ramp and pulse-width trigger, it allows you to trigger on the Y- and Z-sus outputs. Plus you can set it up to record, and play back glitches later, if you have e.g. a TV that blanks out once every hour, it'll capture that.

**aaronwt6** · 12-11-2014, 08:35 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

The DS1054Z looks really nice. I don't know if anyone can swing that for me for a present but I'm going to consider it in the near future. Thanks again for the recommendation.

If I'm going to buy one, I'd certainly like it to do everything it needs to. I always hate the feeling of, 'oh, I wish I had gotten something better'

**Alastair E** · 12-11-2014, 09:07 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

If you can find one--One of the Tektronix 24xx series would be good....

I got one fairly recently --a Tek 2465 450MHz, 4 ch, with cursors and other toys that cost me £15, Had a simple fault--Caps in the PSU which let go the first time I fired it up. --Mains-filter cap, one of those 'RIFA' ones that go smoking....

**tom66** · 12-11-2014, 09:25 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Yes, a very nice scope. Very heavy, though!

My first scope was a HP54501A... but I regret buying a cheap digital HP... I should have bought the Philips PM3394 next to it for the same price.

**aaronwt6** · 12-11-2014, 10:37 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Originally posted by Alastair E View Post

If you can find one--One of the Tektronix 24xx series would be good....

I got one fairly recently --a Tek 2465 450MHz, 4 ch, with cursors and other toys that cost me £15, Had a simple fault--Caps in the PSU which let go the first time I fired it up. --Mains-filter cap, one of those 'RIFA' ones that go smoking....

I'll take a look at those as well. Juts read through the PDP guide in your sig. Quite interesting. Just makes you realize how little it takes to have a problem on any piece of electronics. Not to mention the amount of time and knowledge that goes in to the development.

**Alastair E** · 12-11-2014, 10:54 AM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Originally posted by tom66 View Post

Yes, a very nice scope. Very heavy, though!

My first scope was a HP54501A... but I regret buying a cheap digital HP... I should have bought the Philips PM3394 next to it for the same price.

Heavy......

Nah--It aint heavy, Not in comparison to my old Tek 454 150MHz dual-channel...

--That has Valves in it--well, tiny ones called Nuvistors--All you guys prolly never seen or heard of Nuvistors...Marvellous things!.....

Even managed to get a brand-new CRT for that old 454, but these days,--its showing its age in other ways, needs some serious work to the sync and timebase stages--at least the trace is very bright and sharp though, when it does sync up

**ANDRASONI LUCIAN** · 12-11-2014, 12:20 PM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Check the ZSUS board, change electrolytic caps.From Romania, all the best!

**Alastair E** · 12-11-2014, 02:50 PM

Re: LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

Recently, I had a similar looking fault on an LG 50PK590....

The SET_Up preset did absolutely nothing, and the MOSFET associated with the SET_Up was stone cold.

I traced as far as I could with the drive to this device,--which appeared to be present, but the SET_Up ramp part of the Y-SUS wave was distorted and not very high amplitude.

Tracing back from the gate connection there was a circuit comprising a couple of transistors, and a couple of opto-couplers.
All these devices appeared good. I couldn't go much further as I had no schematic--as none is available....

As the Y-SUS was dirt cheap, I replaced it complete--which solved the problem...
On the replacement board, That said same MOSFET for the SET_Up ramp--was the hottest on the board......

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LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

LG Plasma model 42PC3D Repaired Y-SUS but still have an issue

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